Polymer electrolyte fuel cells bipolar plates

There has been an accelerated interest in polymer electrolyte fuel cells within the last few years, which has led to improvements in both cost and performance. Development has reached the point where motive power applications appear achievable at an acceptable cost for commercial markets. Noticeable accomplishments in the technology, which have been published, have been made at Ballard Power Systems. PEFC operation at ambient pressure has been validated for over 25,000 hours with a six-cell stack without forced air flow, humidification, or active cooling (17). Complete fuel cell systems have been demonstrated for a number of transportation applications including public transit buses and passenger automobiles. Recent development has focused on cost reduction and high volume manufacture for the catalyst, membranes, and bipolar plates. 

Wang, H., and J. A. Turner. 2004. Investigation of a duplex stainless steel as polymer electrolyte membrane fuel cell bipolar plate material. Journal of Power Sources. 128 193-200. 

Polymer Electrolyte Membrane (PEM) fuel cell bipolar plates, discussion of the difficulties associated with confronting bipolar plate development... 

Silva, R.R et al., Surface conductivity and stability of metallic bipolar plate materials for polymer electrolyte fuel cells, Electrochim. Acta, 51, 3592, 2006. 

Fig. 2. Components of a single polymer electrolyte fuel cell used for laboratory investigations. In a stack, relatively thinner current collectors will become bipolar plates with the flow fields machined on both sides.

A polymer electrolyte fuel cell stack with 100 cells and graphite-based bipolar plates is shown in a partly expanded view in Fig. 8.9. 

Figure 18.1. Schematic of a single polymer electrolyte fuel cell, (1) bipolar plates (2) current collectors (3) gas-diffusion layers (4) catalytic layers (5) membrane.

Schonbauer, S., Kaz, T., Sander, H., and Gulzow, E. (2003) Segmented bipolar plate for the determination of current distribution in polymer electrolyte fuel cells, in 2nd European PEFC Forum 2003, Luceme/Switzerland, Proceedings, vol. 1, pp. 231-237. 

Hartnig C, Schmidt TJ (2011) On a new degradation mode for high-temperature polymer electrolyte fuel cells how bipolar plate degradation affects cell performance. Electrochim Acta 56(ll) 4237-4242... 

Polymer Electrolyte Fuel Cells, Mass Transport, Fig. 2 Mass transport through the cathode GDL, interconnecting the channel of the bipolar plate and the catalyst layer... 

Stack Components In collaboration with partners, research and develop technologies to overcome the most critical technical hurdles for polymer electrolyte fuel cell stack components for both stationary and transportation applications. Critical technical hurdles include cost, durability, efficiency, and overall performance of components such as the proton exchange membranes, oxygen reduction electrodes, advanced catalysts, bipolar plates, etc. 

Singdeo D, Dey T, Ghosh PC (2014) Contact resistance between bipolar plate and gas diffusion layer in high temperature polymer electrolyte fuel cells. Int J Hydrogen Energy 39 987-995... 

FIGURE 6.11 Relation between the current density-potential curve against the RHE (reversible hydrogen electrode) of stainless steel (left) and anode and cathode polarization curve of a polymer electrolyte fuel cell (right). (With kind permission from Springer Science+Business Media, Polymer Electrolyte Fuel Cell Durability. Influence of metallic bipolar plates on the durability of polymer electrolyte fuel cells. 2009. pp. 243-256. Scherer, J., Munter, D., and Strobel, R.)... 

Mitani, T. and Mitsuda, K. 2009. Durability of graphite composite bipolar plates. In Polymer Electrolyte Fuel Cell Durability, eds. F. N. Biichi, T. J. Schmidt, and M. Inaba, pp. 257-270. Springer Science + Buisness Media, LLC, New York, NY. 

Nam, D.-G. and Lee, H.-C. 2007. Thermal nitridation of chromium electroplated AISI316L stainless steel for polymer electrolyte membrane fuel cell bipolar plate. Journal of Power Sources 170 268-274. Nam, N. D., Han, J. H., Tai, P. H. et al. 2010. Electrochemical properties of TiNCrN-coated bipolar plates in polymer electrolyte membrane fuel cell environment. Thin Solid Films, doi 10.1016/j. 

Wang, H., Brady, M. R, Teeter, G. et al. 2004. Thermally nitrided stainless steels for polymer electrolyte membrane fuel cell bipolar plates Part 1 Model Ni-50Cr and austenitic 349TM alloys, lournal of Power Sources 138 86-93. 

For most polymer electrolyte fuel cell (PEFC) systems, unit cells are combined into a PEFC stack to achieve the voltage and power output level required for the appUcation. The unit cells normally use a membrane electrode assembly, consisting of a sohd polymer electrolyte with an associated gas-diffusion layer sandwiched between two bipolar plates. The bipolar plates make connections over the entire surface of one cathode and the anode of the next cell. These bipolar plates serve several functions simultaneously (1) they create channels for fuel, air, and water, (2) they separate the unit cells in the stack, (3) they carry current away from the cell, and (4) they support the membrane electrode assembly (Lee et al. 2006 Shao et al. 2007). 

Fig. 12 Long-term performance of a polymer electrolyte fuel cell stack using the graphite composite bipolar plate...

Influence of Metallic Bipolar Plates on the Durability of Polymer Electrolyte Fuel Cells... 

Abstract This chapter describes the behavior and stability of metallic bipolar plates in polymer electrolyte fuel ceU application. Fundamental aspects of metallic bipolar plate materials in relation to suitability, performance and cell degradation in polymer electrolyte fuel cells are presented. Comparing their intrinsic functional properties with those of carbon composite bipolar plates, we discuss different degradation modes and causes. Furthermore, the influence and possible improvement of the materials used in bipolar plate manufacturing are described. 

Wang, H., Sweikart, M. A. and Turner J. A. (2(X)3) Stainless steel as bipolar plate material for polymer electrolyte membrane fuel cells. J. Power Sources 115, 243-251 Wang, X., Kumar, R. and Myers, D. J. (2006) Effect of voltage on platinum dissolution -Relevance to polymer electrolyte fuel cells. Electrochem. Sohd-State Lett. 9, A225-A227 Wang, H., Turner, J. A., Li, X. and Bhattacharya, R. (2007) SnOj F coated austenite stainless steels for PEM fuel cell bipolar plates. J. Power Sources 171, 567-574 Wind, J., Spah, R., Kaiser, W. and Bohm, G. (2002) MetaUic bipolar plates for PEM fuel cells. J. Power Sources 105, 256-260... 

The polymer electrolyte membrane fuel cell (PEMFC) also known as proton exchange membrane fuel cell, polymer electrolyte fuel cell (PEFC) and solid polymer fuel cell (SPFC) was first developed by General Electric in the USA in the 1960 s for use by NASA in their initial space applications. The electrolyte is an ion conducting polymer membrane, described in more details in Section 2.2. Anode and cathode are bonded to either side of the membrane. This assembly is normally called membrane electrode assembly (MEA) or EMA which is placed between the two flow field plates (bipolar plates) (Section 2.5) to form what is known as stack . The basic operation of the PEMFC is the same as that of an acid electrolyte cell as the mobile ions in the polymer are or proton. 

As documented in and expressed by these various contributions, the topic Polymers for Fuel Cells is a vast one and concerns numerous synthetic and physico-chemical aspects, derived from the particular application as a solid polymer electrolyte. In this collection of contributions, we have emphasized work which has already led to tests of these polymers in the real fuel cell environment. There exist other synthetic routes for proton-conducting membrane preparation, which are not discussed in this edition. Furthermore, certain polymers are utilized as fuel-cell structure materials, e.g., as gaskets or additives (binder, surface coating) to bipolar plate materials. These aspects are not covered here. 

Figure 4.1 shows a schematic of a typical polymer electrolyte membrane fuel cell (PEMFC). A typical membrane electrode assembly (MEA) consists of a proton exchange membrane that is in contact with a cathode catalyst layer (CL) on one side and an anode CL on the other side they are sandwiched together between two diffusion layers (DLs). These layers are usually treated (coated) with a hydrophobic agent such as polytetrafluoroethylene (PTFE) in order to improve the water removal within the DL and the fuel cell. It is also common to have a catalyst-backing layer or microporous layer (MPL) between the CL and DL. Usually, bipolar plates with flow field (FF) channels are located on each side of the MFA in order to transport reactants to the... 

Cho, E. A., U. S. Jeon, H. Y. Ha, et al. 2004. Gharacteristics of composite bipolar plate for polymer electrolyte membrane fuel cells. Journal of Power Sources 125 178-182. 

Wolf, H. and Willert-Porada, M., Electrically conductive LCP-carbon composite with low carbon content for bipolar plate application in polymer electrolyte membrane fuel cell, J. Power Sources, 153, 41, 2006. 

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